In recent years treatment of aneurysms has been performed prior to aneurysm rupture and has included the use of stent grafts that are implanted within the vascular system with minimally invasive surgical procedures and that include one or more stents affixed to graft material. The stent grafts are secured at a treatment site by endovascular insertion utilizing introducers and catheters, whereafter they are enlarged radially and remain in place by self-attachment to the vessel wall. In particular, stent grafts are known for use in treating descending thoracic and abdominal aortic aneurysms where the stent graft at one end defines a single lumen for placement within the aorta and at the other end is bifurcated to define two lumens, for extending into the branch arteries.
One example of such a stent graft is disclosed in PCT Publication No. WO 98/53761 in which the stent graft includes a sleeve or tube of biocompatible graft material such as Dacron™ polyester fabric (trademark of E. I. DuPont de Nemours and Co.) or polytetrafluoroethylene defining a lumen, and further includes several stents secured therealong, with the stent graft spanning the aneurysm extending along the aorta proximally from the two iliac arteries; the reference also discloses the manner of deploying the stent graft in the patient utilizing an introducer assembly. The graft material-covered portion of the single-lumen proximal end of the stent graft bears against the wall of the aorta above the aneurysm to seal the aneurysm at a location that is spaced distally of the entrances to the renal arteries. Thin wire struts of a proximal stent extension traverse the renal artery entrances without occluding them, since no graft material is utilized along the proximal stent while securing the stent graft in position within the aorta when the stent self-expands. An extension is affixed to one of the legs of the stent graft to extend along a respective iliac artery and, optionally, extensions may be affixed to both legs. Another known stent graft is the Zenith AAA stent graft sold by William A. Cook Australia Pty. Ltd., Brisbane, Queensland, AU.
Because of life threatening time constraints, such conventional stent grafts are not practical to be utilized with ruptured aneurysms, which presently must be treated, if at all, by open surgery.
Despite the multitude of advances in surgical management and intensive care, the devastating physiological effects of emergency aortic surgery for either ruptured abdominal aortic aneurysms (RAAA) or symptomatic abdominal aortic aneurysms (SAAA), carry an unacceptably high morbidity and mortality rate. Most patients who suffer from RAAA and SAAA are typically unaware of their aneurysmal disease prior to the development of symptoms of actual or impending rupture. The acuity of an RAAA precludes complex radiographic evaluation, does not allow for adequate preoperative planning, and is compounded by the relative unavailability of endovascular stent grafts. Additionally, because of the rapid blood loss from the patient, any substantial surgical delay cannot be tolerated. Another complication stems from the statistical fact that most patients who suffer RAAA or SAAA are elderly and have factors that preclude repair of the rupture by open surgery, with the result that patient mortality from RAAA is very high. Approximately 15,000 deaths per year occur in the United States from ruptured abdominal aortic aneurysms.
Conventional surgical repair of ruptured and symptomatic aneurysms is itself associated with significant complications. Cardiopulmonary complications as a result of a prolonged abdominal operation, significant blood loss and aortic cross clamping, multiple blood transfusions, and hypothermia are most frequently encountered. Mortality of ruptured aneurysms is currently estimated to be between 50% and 75%.
It is thus desired to provide medical devices enabling emergency endovascular treatment of RAAA and SAAA. It is further desired to provide such devices in a manner not requiring, on site at a surgical treatment center, a large inventory of different size devices while still enabling immediate treatment of a large range of aneurysm sizes, nor in a manner requiring preoperative study of the treatment site taking a substantial length of time in order to optimize the selection of an appropriate device. It is yet further desired to provide a medical device that is quickly deliverable and effectively deployable at the treatment site.